Diffraction mechanism in which a monochromator diffracts the X-ray beam in planes transverse to an axis of specimen rotation



y 1968 T. c. FURNAS. JR 3,394,

HANI SM IN WHICH X-RAY DIFFRACTION MEC MONO X TOR DIFFRACTS THE X-RAY AMIN PLA TR VER AN A OF SPECIM ROTATION Filed June 28, 1965 5 Sheets-Sheetl INVENTOR. THOMAS C. FURNAS JR.

ATTORNEYS.

July 23, 1968 T c. FURNAS. JR 3,394,255

X-RAY DIFFRACTION MECHANISM IN WHICH A MONOCHROMATOR DIFFRACTS THE X-RAYBEAM IN PLANES TRANSVERSE TO AN AXIS OF SPECIMEN ROTATION Filed June 28,1965 5 Sheets-$heet 2 Fig. 3

INVENTOR. THOMAS C. FURNAS JR.

ATTORNEYS July 23, 1968 T. c. FURNAS. JR 3,394,

X-RAY DIF'FRACTION MECHANISM IN WHICH A MONOCHROMATOR DIFFRACTS THEX-RAY BEAM IN PLANES TRANSVERSE TO AN AXIS OF SPECIMEN ROTATION FiledJune 28, 1965 3 Sheets-Sheet 5 L ms T w M willl m HI #r D T I L IIIIRRHWr| J KW. llll Ill DI ll UK r h WIILIIWL L 5 1 4 3 5% wk 1 2 |1 L MN z QII I w w w w HM nun u-u-uu------- INVENTOR THOMAS C. FURNAS JR.

ATTORNEYS United States Patent 3,394,255 DIFFRACTIQN MECHANISM IN WHICHA MONO- CHROMATOR DIFFJRACTS THE X-RAY BEAM 1N PLANES TRANSVERSE TO ANAXIS OF SPECIMEN ROTATION Thomas C. Furnas, Jr., Cleveland Heights,Ohio, assignor, by mesne assignments, to Picker Corporation, WhitePlains, N.Y., a corporation of New York Filed June 28, 1965, Ser. No.467,214 19 Claims. (Cl. 250-515) ABSTRACT OF THE DISCLOSURE An X-raydiffraction mechanism in which a monochromator diffraction X-ray beam isutilized. Each characteristic X-ray wavelength is diffracted a differentand characteristic amount than other wavelengths such that the beam isseparated into planes of radiation each of one characteristicwavelength. The planes are transverse to an axis of specimen rotation.The disclosure also includes a method of conducting X-ray diffractionstudies with the X-ray planes so diffracted.

This invention relates to X-ray diffraction and more particularly to anovel and improved process and apparatus utilizing monochromatorcrystals for conducting X- ray diffraction studies.

In X-ray diffraction, it is customary to position a specimen forrotation about an axis known as the theta or the omega axis, and torotate the specimen through an angle known alternately as theta oromega. As the specimen is rotated, it is irradiated with a beam ofX-rays which is diffracted by the specimen. Customarily as the specimenis rotated through an angle theta the rays diffracted by the specimenare detected and then suitably recorded.

The primary beam emitted by an X-ray tube is a mixture of X-rays ofvarious wave lengths. In the past some studies have been conducted inwhich the primary beam is directed against a monochromator crystal (orruled grating) which monochromator diffracts the primary beam toward andthereby irradiates the specimen. As the primary beam is diffracted fromthe monochromator, each wave length is diffracted in a differentdirection so that the X- rays from the monochromator which strike thespecimen (because it is small) are of substantially a single wavelength.

In the past where monochromators have been used to provide a virtualsource of monochromatic X-rays, the monochromator has been positioned sothat X-rays have been ditiracted in planes which are parallel to thetheta axis. The dispersion of X-rays of various wave lengths resultingfrom the monochromator diffraction is known as spectral dispersion. Inthese prior arrangements the spectral dispersion has been perpendicularto the theta axis and, therefore, in the plane of rotation about thetheta axis. Similary, the so-called plane of diffraction of themonochromator has been perpendiuclar to the theta axis. While thisarrangement has provided beams essentially of the desired andappropriately defined wave length spread for irradiating the specimenfor many diffraction experiments, it has many shortcomings when used inother diffraction experiments. This is particularly true with thoseexperiments concerned with the collection of sets of integratedintensities for the purpose of crystal structure determination, andthose concerned with powder diffrac tometry. These shortcomings includeat least the followmg:

(1) It must be recognized that the specimen itself is a "ice crystal.When the specimen is parallel to the monochromator, the dispersions ofrays diffracted by the two crystals are opposite and offset one another.When the specimen is anti-parallel; the dispersions are additive. Forthis reason there is an asymmetry of geometry and type of diffractionfor reflections from the specimen which occur as the specimen is rotatedclockwise or counterclockwise about the theta axis from a given positionbetween the parallel and anti-parallel positions. This asymmetry is soimportant that it is recognized by special names which describe theparallel (1, 1) and the anti-parallel (1,1) reflecting positions.

(2) There is an error (often indeterminant) in the integrated intensitymeasurement due to the fact that the radiation from the monochromator isdirected and not diffuse. Thus, the radition is dispersed spatially bywave length and unable to irradiate all parts of the specimen uniformlyand identically in wave length and intensity. This error is magnified byits simultaneous occurrence with the asymmetry mentioned above.

(3) There is a general inability for extreme inconvenience to change theangular divergence of X-rays striking the specimen from the primarysource as seen in virtual image through the monochromator. It isdiflicult or impossible to accommodate the very different geometriesdesired for (a) searching for reflection from the specimen; (b)stationary intensity measurements; (c) scanning intensity measures; and,(d) determination of lattice parameters and mosaic spread. These too areaggravated bv the asymmetry described above.

(4) A closely related problem is that it is extremely diffcult to alignthe X-ray tube, the monochromat-or, the specimen, and the detector. Thisis true because the asymmetry described above makes the reflection verynarrow. It is also true because true optimum positioning requires amultitude of scans since it is practically impossible to get all of thespecimen to diffract at once.

-(5) Some studies are made in a plus two-theta region; i.e., clockwisefrom a plane located by the theta axis and the source of X-rays excitingthe specimen. Other studies are made in a region which iscounterclockwise from this plane and known as minus two-theta, There isconsiderable uncertainty and error both in the interpretation of thedata that might be collected and in accounting for the unequal scanranges involved in the measurement and comparison of the plus two-thetareflections and minus two-theta reflections because of the asymmetrymentioned above. Although no designation has been officially specifiedin the literature it will be convenient to refer to the parallel (1, 1)position as belonging to the positive two-theta region since this is theone most commonly employed. While there generally is negligibleasyminetry to a direct X-ray source this terminology agrees with thegeneral assertion that the positive two-theta region is that permittingthe largest two-theta range and this usually places the X-ray tube anodesurface and the specimen diffracting planes in the parallelconfiguration to one another.

(6) The dispersion calculation and corrections are different in thepositive and in the negative two-theta regions due to the asymmetrymentioned above.

(7) In the past, the obtainment of higher intensity monochromaticX-irradiation of the specimen has been attempted or achieved bycylindrically curving the monochromator about an axis parallel to thetheta (or omega) axis. When this is done, the angular range throughwhich the specimen must be rotated to pass entirely through itsreflecting position is increased. Although no special designation hasbeen given in the literature, it appears appropriate to use (C, 1) forthe curved parallel reflecting position and (0,1) for the curvedanti-parallel reflecting position to emphasize that complications due toasymmetry still exist.

(8) In powder diifractometry it is necessary to use soller slits in theX-ray beam between the monochromator and the specimen to limit thedivergence along the theta axis. The vanes of the soller slit areperpendicular both to the theta axis and to the diffracting planes ofthe monochromator in the common arrangement described above.

Asymmetry is of considerable importance as is demonstrated by itspresence in six of the above list of eight short-comings experiencedwith the commonly employed arrangement. Accordingly, it should beconsidered in further detail.

In the parallel (1, -1) position the clilfracting planes of themonochromator are parallel to the ditfracting planes of the specimen.(Actually 6 0 where O is the diffraction angle at the monochromator anda the diffraction angle at the specimen.) Strict parallelism is achievedwhen the diffraction angles of the crystal and monochromator are equal.When this is true then all the wave lengths diffracted from themonochromator are simultaneously diffracted from the specimen. Thus, thespectrum dispersed by the monochromator is recombined by reflection fromspecimen planes in the parallel (1, position. The angular Width of thereflection measured by rotation of the specimen about two-theta or omegaaxis generally is called the instrument width as it somewhatcharacterizes (a) the sizes of apertures; (b) the mosaicity of themonochromator and of the specimen; (c) the net angular convergence ofX-rays upon the specimen; and, (d) the ability of the specimen todiffract X-rays.

In the position where the diffracting planes of the monochromator andspecimen crystals are antiparallel, the planes are at 0 +0 When this istrue then only one wave length at a time is diffracted from thespecimen. Thus, the spectrum dispersed by the monochromator is furtherdispersed by reflection from specimen planes in the anti-parallel (1, 1)position.

In single crystal structure analysis it often is very important to beable to measure the intensities of reflection in certain positions inthe plus two-theta region and compare them with the correspondingintensities of reflection measured in the minus two-theta region. Theseare related to one another as are the front and back of a mirror. A veryconvenient means for making these measurements is to make one clockwiseand the other counterclockwise about the theta axis. These are,therefore, precisely the parallel and anti-parallel positions mentionedearlier so the importance of any anomalies, differences or asymmetry ofthe measurements becomes greatly magnified. These measurements arecommonly referred to as being made in the positive or plus two-thetaregion and in the negative or minus two-theta region.

With the present invention, these shortcomings and anomalies areovercome by providing a construction wherein the dispersion from themonochromator is specifically parallel to the omega, theta axis ofrotation of the specimen. Thus, each Wave length of X-ray energy is in aplane which is transverse to the omega, theta axis. Because of thisresultant spectra are obtained at both plus and minus two-theta whichare equal and opposite. Although it is preferable that the dispersion ofthe specimen be perpendicular to the omega, theta axis of specimenrotation (the socalled equatorial diffraction geometry), the generaladvantages of the present invention are equally obtained in theWeissenberg or upper lever diffraction geometries. In particular, theLorentz, polarization and dispersion correction for a particularreflection whether it is observed in the positive or negative twothetaregion are the same. In stationary specimen intensity measurementtechniques this invention is also beneficial. This is true because thespecimen will diffract in a manner which permits many stationary studiesto be 4 conducted where in the past specimen rotation has been required.

As noted above, with this invention, the spectral dispersion of themonochromator is parallel to the omega, theta axis and, therefore,perpendicular to the plane of rotation about the coincident omega, thetaaxis. To distinguish this arrangement from the one used in the past andto emphasize its symmetrical character the terminology planeperpendicular (l, P) is proposed to describe the use of a plane grating,plane reflection crystal or a plane transmission crystal as themonochromator oriented with its dispersion perpendicular to the specimenrotation axis or specimen dispersion. The terminology curvedperpendicular (C, P) is proposed to describe the use of a curvedgrating, curved reflection crystal or curved transmission crystal as themonochromator oriented with its dispersion perpendicular to the specimenrotation axis or specimen dispersion.

With this invention, the primary source of X-radiation is positioned toone side of the monochromator away from the specimen. The primary sourceis above or below the monochromator when the omega, theta axis isvertical. The rays are directed at the monochromator at an angle suchthat a diffracted beam of a selected wave length is directed to thespecimen.

In addition to the advantages of overcoming all of the above-listedproblems, a construction of the improved type has the effect of allowingthe divergence of X-rays irradiating the specimen to be changed readilyby changing the take-off angle to the X-ray tube target. This can bedone without effecting the monochromaticity of the beam striking thespecimen.

Another advantage of this arrangement where a line rather than a spotsource is used, it is possible to eliminate the soller slit assemblybetween the X-ray source and the specimen without disturbing thefocusing properties useful in the plane of diffraction or measurement.This is especially true where the specimen is a powder. Either a sollerslit or a second (1, P) monochromator arrangement can be used betweenthe specimen and the detector. In this case it is desirable that the twomonochromators bear a parallel (l, -l) relationship to one another.

Accordingly, the objects of the invention are to provide a novel andimproved difiractometer utilizing a monochromator and a method ofconducting diffraction studies.

Other objects and a fuller understanding of the invention may be had byreferring to the following description and claims taken in conjunctionwith the accompanying drawings in which:

In the drawings:

FIGURE 1 is a perspective view of a diffractometcr made in accordancewith this invention;

FIGURE 2 is an elevational view, on an enlarged scale with respect toFIGURE 1, of the novel tube and monochromator crystal support mechanismof this invention with parts broken away and removed;

FIGURE 3 is an end elevational view of the device and scale of FIGURE 2,as seen from the plane indicated by the line 33 of FIGURE 2, and withparts broken away and removed;

FIGURE 4 is a top plan view of the structure and scale of FIGURE 2;

FIGURE 5 is an end elevational view of the structure and scale of FIGURE2 as seen from the plane indicated by the line 5-5 of FIGURE 2; and,

FIGURE 6 is a sectional view, on an enlarged scale With respect toFIGURE 2, of the crystal support, as seen from the plane indicated bythe line 66 of FIG- URE 2.

In FIGURE 1, a diffractometer is shown generally at 10. Thediffractometer It is preferably of the type described and claimed incopending application Ser. No. 236,468, filed Nov. 2, 1962, which is nowUnited States Patent 3,218,458 issued Nov. 16, 196 5, T. C. Furnas, Jr.and entitled Diffractometer. The diffractometer includes a housing 11. Atwo-theta member 12 is journaled in the housing 11 for rotation about atheta axis. Assuming the housing 11 is horizontal, the theta axis is avertical axis which intersects the specimen, as will become moreapparent from the subsequent description.

A two-theta arm 13 is secured to the two theta member 12. The two-thetaarm 13 supports the usual detector 15 and slit structure 16. A cone-likecollimator structure 17 is also secured to the two-theta arm 13 forcollimating rays diffracted by a specimen before they pass through theslit 16 into a detector 15.

A goniometer is shown generally at 20. The goniometer pictured is one ofthe type described and claimed in detail in US. Patent 3,189,741 issuedJune 15, 1965 to George V. Patser under the title Goniostat. Thegoniostat 20 is mounted on a theta member 21 for rotation about theomega, theta axes.

The goniostat 20 includes a phi head 22 which supports a'specimen S at aposition along the omega, theta axes. The specimen S is also located ona chi axis which is the horizontal axis of the goniostat 20 when thehousingll is horizontal. The phi head 22 is orbital about the chi axisand equipped to selectively rotate the specimen S about a phi axis. Asis indicated by the preceding discussion, the chi axis is perpendicularto and intersects the omega, theta axes at the point where the specimenis rotated. Similarly, the phi axis intersects these axes at the samepoint and is also perpendicular to the chi axis. A phi axis may'be anyradius of the goniostat perpendicular to the chi axis. An eye piece 23is secured to the goniostat 20 and positioned for use in locating thespecimen S precisely at the intersection of these axes.

A pair of X-ray tube support pedestals 25, 26 are fixed to the housing11. An X-ray tube and monochromator assembly is shown generally at 30.The assembly 30 is secured to the pedestals 25, 26 as by bolts 31. Theassembly 30 will be best understood by reference to FIGURES 2-6.

The assembly 30 includes a base 32 which is the element of the assemblythat is fixed to the pedestals 25, 26 by the bolts 31. The base 32includes an upstanding arm 33 which is at the right hand end of the baseas viewed in FIGURE 2. The upstanding arm 33 extends longitudinally ofthe base 32 and provides a support for monochromator and X-ray tubepivots as will become apparent presently. The base includes a secondupstanding arm 34 which is at the left hand end of the base as viewed inFIGURE 2. The second upstanding arm 34 is transverse with respect to thebase 32 and supports the mechanism for causing adjustment pivoting theX-ray tube about a crystal axis as will also become more apparentpresently.

A rigid pivot support arm 35 is secured to the base arm 33 extendingupward from the base and outward toward the goniostat 20. A steppedcrystal and tube Support shaft is provided at 37. The crystal and tubesupport shaft 37 is rotatably supported in the pivot arm 35 by small andlarge bearings 38, 40. A Washer 41 is clamped against one race of thesmall bearing 38 by a nut 42 Which threads on one end of the shaft 37.The support shaft,37 includes an enlarged part 43 which engages a raceof the large bearing so that the bearings 3840 serve not only to journalthe support shaft 37 but also as thrust bearings to locate it axially.

An X-ray tube support member 45 is provided. The support member 45extends longitudinally with respect to the base 32. The support member45 includes an upstanding pivot arm 46 at its right hand end as seen inFIGURE 2. The pivot arm 46 is journaled by a bearing 47 on an endportion 48 of the support shaft 37. The end portion 48 is at the righthand end as seen in FIG- URE 2. An examination of FIGURE 2 will showthat the tube support base 45 is pivotal about the axis of the supportshaft 37. The mechanism for adjusting the tube support base 45 about theaxis of the support shaft 37 will be described below.

An X-ray tube housing 50 is shown in solid lines in FIGURES 1 and 3 andindicated in phantom in FIG- URES 2, 4, and 5. The X-ray tube housing 50includes a focal spot end portion 51 of reduced size. The end portion 21is square in cross section and houses the X-ray tube target. The targetis indicated in dotted lines at 53 in FIGURE 2.

A spherical bearing support assembly is shown gen erally at 54. Thissup-port assembly 54 secures the focal spot end portion 51 of the X-raytube housing 50 to the X-ray tube base 45. The spherical bearing supportassembly 54 is of the type described in detail in the above-referencedcopending application for a diffractometer. As an examination of FIGURE3 Will show, the spherical bearing shown in dotted lines at 55 isimmediately below the focal spot of the target 53.

A knurled head 57 of a take-off angle adjustment screw is visible inFIGURES 1 and 2. A portion of the adjustment screw is visible at 58 inFIGURE 1. The take-off angle adjustment is of the type described in theabovereferenced patent application. The adjustment screw 58 threadablyengages the X-ray tube housing 50 to shift it transversely with respectto the base 45 and adjust the take-off angle about the axis of thespherical bearing 55.

A pivot adjustment arm 60 extends upwardly from and forms one end of theX-ray tube support bracket '45. The pivot adjustment arm 60 is at theleft hand end of the bracket 45 as viewed in FIGURES 2 and 4. Anarcuately curved pivot control shoe 61 is secured to the upstanding arm60 as by bolts 63. An arcuately curved lower surface 64 of the shoe 61rides on a pair of rollers 65 secured to the base arm 34. A hold-downroller 66, FIG- URES 2 and 4, rides on an upper arcuate surface 67 ofthe shoe 61. The hold-down roller 66 is also secured to the arm 34.Coaction of the rollers 65, 66 with the shoe 31 causes any relativemovement to be along an arcuate path.

A worm gear 70 is secured to the arm 60 and the shoe 61 by the bolts 63.A worm 71 engages the worm gear 70 such that rotation of the worm 71will cause arcuate movement of the worm gear 70 and the connectedmechanism. Thus, rotation of the worm 70' will cause rotation of theX-ray tube about the axis of the support shaft 37.

An odometer 72 is secured to the base 32 and connected to the worm 71 bya worm shaft 73. Rotation of odometer handles 74 will cause rotation ofthe shaft 73 and thus pivotal adjustment movement of the X-ray tubeabout the axis of the support shaft 37. The odometer is provided so thatone can determine the amount of adjustment movement of the X-ray tubeabout the axis of the support shaft 37.

Referring now to FIGURES 2 and. 6 in particular, a semi-cylindricalsegment 75 is cut out of the section 43 of the support shaft 37. Amonochromator crystal 76 is positioned in a recess 77 in the section 43so that the monochromator crystal is disposed with its reflectingsurface along the axis of the support shaft 37, and immediately belowthe segment 75.

The segment 75 is closed by a primary beam arcuately curved clip 79 anda diffracted beam arcuately curved clip 80. It should be noted here thatfor clarity of illustration the clips 79, 80 are not visible in any ofthe figures other than FIGURE 6. The primary beam clip 79' has a pair ofarcuate recesses 81 which receive the clip 80 and permit relativerotation of the two clips. The two clips overlap and surround the shaftportion 43 between the bearings 40, 47, so that the segment 75 iscompletely closed except for apertures 82, 83 in the clips 79, 80respectively.

The X-ray tube is preferably equipped with shutters of the typedescribed and claimed in detail in US. Patent No. 3,113,214, issued toT. C. Furnas, In, on Dec. 3, 1963, under the title of DitfractometerShutter. This shutter engages an insert 84 which defines the aperture 32of the clip 81. Thus, the clip 84 and the shutter together define anX-ray pervious passage which collimates and conducts the primary X-raybeam from the target 53 of X-ray tube to the monochromator crystal 76.Rays diffracted by the monochromator crystal 76 pass through theaperture 83 0f the clip 8t) and into a collimating structure 85. Thesediffracted rays pass through the collimating structure 85 and are thencedirected against the specimen S.

In alignment of the X-ray tube and the monochromator crystal, someadujstment of the crystal may be desired. Accordingly, a disc 90 issecured to the end of the support shaft 37 opposite the washer 41. Anadjustment lever 91 is secured to the disc 9! A spring 92 acts againstthe lever 9'1 forcing it into engagement with an adjustment set screw93. With this structure the angle of the planes of diffraction of themonochromator crystal '76 can be adjusted by rotation of the set screw93.

Method of operation When the device is operated, a specimen S is firstmounted on the phi member 22. The position of the specimen is adjusteduntil it is located on the cross hairs provided to the eye piece 23.Manual adjustment of the phi, chi, omega, theta, and two-theta anglesabout their respective axes can be accomplished in the manner taught inthe above-referenced patent and application until the specimen isprecisely positioned for a desired study.

The handle 74 of the odometer is rotated until the appropriate angle ofthe primary beam emanated by the X-ray tube to the plane of diffractionof the specimen crystal is obtained. The set screw 93 may be rotated toadjust the plane of the monochromator crystal to its desired attitude.

Once these various adjustments have been made, the X-ray tube isenergized and the shutter opened. The specimen S will be struck bysubstantially a single wave length of X-rays throughout its study andthe specimen will be rotated appropriate amounts about the several axes.While the specimen is being rotated, the detector will be selectivelyrotated about the two-theta axis and, as noted in the introduction,always in the plane of a given and selected wave length of X-rays, dueto the novel positioning of the monochromator crystal. It will beapparent that all but substantially Onewave length of X-rays pass eitherabove or below both the specimen and the detector so that the specimenand detector are acted on by substantially a single wave length.

Although the invention has been described in its preferred form with acertain degree of particularlity, it is understood that the presentdisclosure of the preferred 'form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may 'be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

1. In a mechanism utilizing X-ray energy for the nondestructive testingof a specimen, the combination of:

(a) a support 'for mounting a specimen along an axis;

(b) beam diffraction means mounted in spaced relationship with thesupport and positioned to ditfract X-ray energy divergent in planestransverse to said axis; (0) an X-ray source secured in spacedrelationship with said diffraction means and positioned to direct a beamof X-rays against said diffraction means;

((1) said diffraction means being positioned to diffract portions ofsaid beam toward a mounted specimen; and,

(e) a detector for measuring rays diffracted by a specimen and mountedfor positioning in a plurality of positions in a plane transverse tosaid axis.

2. The device of claim 1 wherein the diffraction means is amonochromator crystal adjustable about an axis which is transverse andspaced from the previously mentioned axis and transverse to said beam.

3. The device of claim 2 wherein the X-ray source is adjustable aboutsaid crystal adjustment axis.

4. The device of claim 1 wherein the X-ray tube assembly is adjustableabout an axis transverse to and spaced from said previously mentionedaxis.

5. In an X-ray mechanism for the non-destructive testing of a specimen,the combination of:

(a) a housing;

(b) a rotatable omega member journaled in said housing and rotatableabout an omega axis;

(c) specimen supporting means mounted on said omega member and includingmeans to support a specimen at a location along said axis;

(d) a crystal mounted on said housing and positioned to diffract X-raysin planes transverse to said omega axis;

(e) an X-ray tube assembly including a focal spot mounted on saidhousing and positioned with said crystal between the focal spot and saidlocation; and,

(f) said X-ray tube assembly including collimating means for delineatinga beam of X-rays directed against said crystal whereby said crystal willdiffract portions of said beam to said location.

6. The device of claim 5 wherein the tube assembly is mounted on thehousing by a supporting structure which includes means to rotate thetube assembly about an axis intersecting the crystal.

7. The device of claim 5 wherein the crystal is mounted on the housingby supporting structure which includes means to rotate the crystal aboutan axis intersecting the crystal.

8. The device of claim 7 wherein said X-ray tube assembly is mounted onthe housing by supporting structure including means to rotate the X-raytube about said crystal adjustment axis.

9. The device of claim 8 wherein the tube assembly is also adjustableabout an axis passing through said focal spot.

10. In a method of conducting an X-ray diffraction study, theimprovement comprising:

(a) diffracting a source of X-ray energy to separate said energy intoplanes of energy of differing wave lengths;

(b) positioning an X-ray specimen in a plane of a selected wave length;and,

(c) rotating a detector means about an omega axis transverse to saidplane and intersecting the specimen while so positioned.

11. The method of claim 10 including the step of adjusting a selectedone of the X-ray source and crystal about an axis intersecting thecrystal and transverse and spaced from the omega axis.

12. In combination:

(a) a diffractometer including theta and two-theta mechanisms rotatableabout a common axis;

(b) a detector mounted on the two-theta mechanism;

(c) a goniostat mounted on the theta mechanism;

(d) a specimen support to mount a specimen on the goniostat;

(e) collimating structure on the two-theta mechanism between thespecimen and the detector for collimating a beam of X-rays diffracted bythe specimen;

(f) first and second pedestals mounted on the diffractometer (on theside of the goniostat opposite said detector);

(g) an X-ray tube and crystal assembly mounted on the pedestals andpositioned to irradiate a specimen on the goniostat, said assemblycomprising:

(i) a base member with first and second spaced upstanding arms;

(ii) a monochromator and X-ray tube pivot support shaft journaled on thefirst arm;

(iii) an X-ray tube support journaled on said pivot support shaft;

(iv) an X-ray tube on said tube support;

(v) X-ray tube rotation adjustment means mounted on the secondupstanding arm and connected to the tube;

(vi) take-off angle adjustment means between said X-ray tube and saidbase member;

(vii) said pivot support shaft including a cutaway segmental portiondefining a crystal opening; and,

(viii) a monochromator crystal mounted in said opening in the path of abeam emanated by said X-ray tube; and,

(b) means to collimate X-rays diffracted by said monochromator crystaland direct the collimated beam against the specimen.

13. In combination:

(a) a diffractometer including theta and two-theta mechanisms rotatableabout a common axis;

(b) a detector mounted on the two-theta mechanism;

(c) a specimen support to mount a specimen on the theta mechanism; and,

(d) an X-ray tube and crystal assembly mounted on the diffractometer andpositioned to irradiate a specimen on the support, said assemblycomprising:

(i) a base member;

(ii) a monochromator and an X-ray tube pivot support shaft journaled onthe base member;

(iii) an X-ray tube support journaled on said pivot support shaft;

(iv) an X-ray tube and housing on said tube sup- (v) X ray tube rotationadjustment means mounted on the base member and connected to the tube;

(vi) said pivot shaft including a cutaway portion defining an opening;and,

(vii) an X-ray diffraction means mounted in said opening in the path ofa beam emanated by said X-ray tube and positioned to diffract X-raystoward said specimen.

14. The device of claim 13 wherein first and second arcuately curvedclips overlie one another and are mounted on said shaft support to closethe perimeter of said opening, said clips respectively including aprimary beam aperture in communication with an opening in the X-ray tubehousing and a diffracted beam aperture positioned to conduct X-raysdiffracted by said diffraction means toward said specimen.

15. The device of claim 13 wherein said X-ray tube adjustment meansincludes a worm gear and a worm.

16. The device of claim 15 wherein an odometer is connected to the worm.

17. The device of claim 13 wherein a means for adjusting the diffractionmeans about the aixs of the support shaft is provided.

18. In a method of conducting an X-ray diffraction study, the improvedsteps comprising:

(a) diffracting a source of X-ray energy to separate said energy intoplanes of energy of differing wave lengths;

(b) positioning an X-ray specimen :in a plane of a selected wave lengthand at an axis transverse to said plane;

(c) successively positioning a detector means in each of a plurality ofpositions in a detector cone about said axis and intersecting thespecimen; and,

(d) detecting radiation diffracted by said specimen with said detectormeans while in each of said plurality of positions.

19. In a method of conducting an X-ray diffraction study, the improvedsteps comprising:

(a) diffracting a source of X-ray energy to separate said energy intoplanes of energy of differing wave lengths;

(b) positioning an X-ray specimen in a plane of a selected wave lengthand at an axis transverse to said plane; and,

(c) detecting radiation diffracted by said specimen with a detectormeans in each of a plurality of positions in a detector cone about saidaxis and intersecting the specimen.

References Cited UNITED STATES PATENTS 3,105,901 10/1963 Ladell et a1250-515 3,213,278 10/1965 Spielberg 250-51.5 3,322,948 5/1967 Baak eta1. 250-515 RALPH G. NILSON, Primary Examiner.

A. L. BIRCH, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 594,255 July 23 1968 Thomas C. Furnas, Jr.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line 21, "for" should read or Column 3,

line 25, "(l,)" should read (l, -1) Column 8, lines 71 and 72, cancel"(on the side of the goniostat opposite said detector)". Column 10, line12, "aixs" should read axis Signed and sealed this 27th day of January1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, 11'.

Commissioner of Patents Attesting Officer

